Trucking is the primary mode of long-distance and short-haul transport for goods and materials in the United States, and many other countries. Trucks typically include a motorized cab in which the driver sits and operates the vehicle. The cab is attached to a box-like cargo section. Smaller trucks typically include an integral cargo section that sits on a unified frame which extends from the front wheels to the rear wheel assembly. Larger trucks often include a detachable cab unit, with multiple driven axles, and a separate trailer with a long box-like cargo unit seated atop two or more sets of wheel assemblies. These truck assemblages are commonly referred to as “semi-trailers” or “tractor trailers.” Most modern trucks' cabs, particularly those of tractor trailers, have been fitted with aerodynamic fairings on their roof, sides and front. These fairings assist in directing air over the exposed top of the box-like cargo body, which typically extends higher (by several feet) than the average cab roof. The flat, projecting front face of a cargo body is a substantial source of drag, above the cab roof. The use of such front-mounted aerodynamic fairings in recent years has served to significantly lower drag and, therefore, raise fuel economy for trucks, especially those traveling at high speed on open highways.
However, the rear end of the truck's cargo body has remained the same throughout its history. This is mainly because most trucks include large swinging or rolling doors on their rear face. Trucks may also include a lift gate or a lip that is suited particularly to backing the truck into a loading dock area so that goods can be unloaded from the cargo body. It is well-known that the provision of appropriate aerodynamic fairings (typically consisting of an inwardly tapered set of walls) would further reduce the aerodynamic profile of the truck by reducing drag at the rear face. The reduction of drag, in turn, increases fuel economy. By way merely of background, one such aerodynamic structure is shown and described in U.S. Pat. No. 6,595,578 entitled TRUCK AFTER-BODY DRAG REDUCTION DEVICE, by Kyril Calsoyas, et al., the teachings of which are expressly incorporated herein by reference.
Nevertheless, most attempts to provide aerodynamic structures that integrate with the structure and function of the rear cargo doors of a truck have been unsuccessful and/or impractical to use and operate. Such rear aerodynamic structures are typically large and difficult to remove from the rear so as to access the cargo doors when needed. One approach is to provide a structure that swings upwardly, completely out of the path of the doors. However, aerodynamic structures that swing upwardly require substantial strength or force to be moved away from the doors, and also require substantial height clearance above an already tall cargo body. Other solutions have attempted to provide an aerodynamic structure that hinges to one side of the cargo body. While this requires less force to move, it also requires substantial side clearance—which is generally absent from a closely packed, multi-truck loading dock.
In fact, most loading dock arrangements require that the relatively thin cargo doors of conventional trucks swing open fully to about 270 degrees so that they can be latched against the adjacent sides of the cargo body. Only in this manner can the truck be backed into a standard-side-clearance loading dock, which is often populated by a line of closely-spaced trailers that are frequently entering and leaving the dock. In such an environment, side-projecting or top-projecting fairings would invariably interfere with operations at the loading dock.
A possible solution is to bifurcate the aerodynamic structure into a left hinged and a right-hinged unit that defines a complete unit when closed, and hinges open to reveal the doors. However, the two separate sections still present a large projection that would be incapable of swinging the requisite 270 degrees, and would undesirably tend to project into the adjacent loading bays when opened.
Another alternative is to remove the fairing structure from the truck before it is parked at the loading bay. However, the removed structure must then be placed somewhere during the loading/unloading process. Because most truck doors are relatively large, being in the range of approximately 7-8 feet by 8-9 feet overall, removing, manipulating and storing a fairing in this manner may be impractical, or impossible, for the driver and loading dock staff.
Many other approached to providing an aerodynamic structure to the rear of a truck trailer body have been proposed. However most lack practicality and/or workability, and would either fail to perform as expected or pose too great an inconvenience to the operator. Nevertheless the need for such an aerodynamic structure is clear.
In the face of ever-increasing fuel costs, it is critical to develop aerodynamic structures that can be applied to the rear of a truck cargo body, either as an original fitment, or by retrofit to existing vehicles. These structures should exhibit durability and long service life, be easy to use by the average operator, not interfere with normal loading and unloading operations through a rear cargo door, and not add substantial additional cost or weight to the vehicle. The structure should exhibit a low profile on the vehicle frame and/or doors, not impede side clearance when the doors are opened, and where possible, allow for clearance with respect to conventional door latching mechanisms. Such structures should also allow for lighting on the rear, as well as other legally required structures. Moreover, given the large existing fleet of trucks and trailers, it is highly desirable that an aerodynamic structure be easily and inexpensively retrofittable to a wide range of existing vehicles without undue customization.